This invention relates to a roller whose outer cylinder is designed to rotate supported by a thin layer of air which works as a pneumatic bearing.
In a conveyor for carrying such comparatively light products as sheets, films, plates and the like, a row of rollers supported in a frame at a certain spacing is used; these rollers are not driven by power but by the feed of products.
Incidentally, an outer cylinder of such conventional rollers is supported by a bearing; however, in order to rotate the rollers, a relatively large moment is required at first in order to overcome the resistance originating therefrom. Therefore, there appears a lag in the rotation of rollers relative to the movement of goods just fed on a conveyor especially when the goods are comparatively light products such as sheets, films, plates, etc. which do not have enough moment to rotate the rollers. As a consequence, slippage occurs between the goods and the rollers, which tends to scratch the goods, especially when they are mirror-finished or printed, and deteriorate their merchandise value. In addition, such structure as the outer cylinder of the rollers is supported by a bearing and needs frequent checks and maintenance.
Under these circumstances, the present inventors have keenly studied to eliminate the drawbacks of the conventional rollers and finally accomplished the present invention.
It is an object of the present invention to provide a roller whose initial resistance to rotation is so little that there arises virtually no slip between goods fed on a conveyor and the surface of the roller. It is another object of the present invention to provide a roller whose performance does not decline so much as to require periodic checks and maintenance.